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PCI/switchtec: Add Gen4 MRPC GAS access permission check

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Gen4 hardware provides new MRPC commands to read and write directly from
any address in the PCI BAR (which Microsemi refers to as GAS). Since
accessing BARs can be dangerous and break the driver, we don't want
unprivileged users to have this ability.

Therefore, require CAP_SYS_ADMIN for the local and remote GAS access MRPC
commands. Privileged processes will already have access to the BAR through
the sysfs resource file so this doesn't give userspace any capabilities it
didn't already have.

[logang@deltatee.com: rework commit message]
Link: https://lore.kernel.org/r/20200106190337.2428-11-logang@deltatee.com
Signed-off-by: Kelvin Cao <kelvin.cao@microchip.com>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
This commit is contained in:
Kelvin Cao 2020-01-06 12:03:35 -07:00 committed by Bjorn Helgaas
parent 4efa1d2e36
commit ce7c88600b
2 changed files with 11 additions and 0 deletions
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6
drivers/pci/switch/switchtec.c
View File

@ -479,6 +479,12 @@ static ssize_t switchtec_dev_write(struct file *filp, const char __user *data,
rc = -EFAULT;
goto out;
}
if (((MRPC_CMD_ID(stuser->cmd) == MRPC_GAS_WRITE) ||
(MRPC_CMD_ID(stuser->cmd) == MRPC_GAS_READ)) &&
!capable(CAP_SYS_ADMIN)) {
rc = -EPERM;
goto out;
}
data += sizeof(stuser->cmd);
rc = copy_from_user(&stuser->data, data, size - sizeof(stuser->cmd));

5
include/linux/switchtec.h
View File

@ -21,6 +21,11 @@
#define SWITCHTEC_EVENT_FATAL BIT(4)
#define SWITCHTEC_DMA_MRPC_EN BIT(0)
#define MRPC_GAS_READ 0x29
#define MRPC_GAS_WRITE 0x87
#define MRPC_CMD_ID(x) ((x) & 0xffff)
enum {
SWITCHTEC_GAS_MRPC_OFFSET = 0x0000,
SWITCHTEC_GAS_TOP_CFG_OFFSET = 0x1000,